1. Field of the Invention
The present invention relates to a webbing retractor equipped with a pretensioner mechanism which eliminates slackness in a webbing at the time of an emergency of a vehicle due to a collision or the like, and a force limiter mechanism which limits the load applied to a vehicle occupant by the webbing to a predetermined amount or less.
2. Description of the Related Art
A webbing retractor is equipped with a pretensioner mechanism which eliminates slackness in a webbing at the time of an emergency of a vehicle due to a collision or the like.
Among such pretensioner mechanisms, there are pretensioner mechanisms using a so-called rack-and-pinion system. In a webbing retractor equipped with a rack-and-pinion-type pretensioner mechanism, a pinion is connected to a take-up shaft which takes-up a webbing, and the pinion always rotates integrally with the take-up shaft. Further, a substantially tube-shaped cylinder is provided in a vicinity of the pinion.
Within the cylinder, a fit-together portion, which is fit tightly with the inner wall of the cylinder, is provided at the lower portion, and a piston, at which a rack is provided, is slidably provided at the upper portion. At the time of an emergency of the vehicle, gas is supplied into the cylinder from beneath the fit-together portion of the piston. In this way, the piston receives the pressure of the gas from beneath, and rises within the cylinder. Due to the piston rising, the rack meshes with the pinion, and the pinion is rotated in the webbing take-up direction. In this way, at the time of an emergency of the vehicle, the webbing is taken-up on the take-up shaft, and the slackness in the webbing is cancelled.
Further, among webbing retractors provided with a pretensioner mechanism as described above, there are webbing retractors equipped with a force limiter mechanism which, at the time of an emergency of the vehicle, and in particular, at the time when a collision force is extremely large, lets out a predetermined amount of the webbing in order to limit the load applied to the vehicle occupant by the webbing to a given amount or less.
Such a force limiter mechanism is provided, for example, with an energy absorbing member. Due to a vehicle occupant receiving a large collision force at the time of an emergency of the vehicle, load is applied to the webbing holding the vehicle occupant. The energy absorbing member is deformed by the load applied to the webbing by the vehicle occupant, and the take-up shaft is thereby rotated in the webbing pull-out direction. In this way, at the time of an emergency of the vehicle, the webbing is pulled-out form the take-up shaft, and the load applied to the vehicle occupant by the webbing is limited to a given value or less.
However, in such a webbing retractor, when the force limiter mechanism is operated, the take-up shaft is rotated in the webbing pull-out direction. Thus, the pinion, which always rotates integrally with the take-up shaft, is also rotated in the webbing pull-out direction. In this way, the rack, which is meshing with the pinion, moves, and the piston falls within the cylinder. Thus, the pressure of the gas within the cylinder (beneath the fit-together portion) rises, and lowering of the piston is impeded. Therefore, a load is applied to the take-up shaft which is rotating in the webbing pull-out direction, and pulling-out of the webbing is impeded.
Accordingly, as shown in FIG. 7, the so-called force limiter load (which is equivalent to the load for the webbing to be pulled out at the time of an emergency of the vehicle) is a load in which the load (the load of the portion marked C in FIG. 7) due to the pressure of the gas in the cylinder (the raised pressure due to the falling of the piston) is added to the load for the energy absorbing member to deform. In this way, a problem arises in that it is difficult to set the force limiter load, and the range of setting is narrow.
In view of the above circumstances, an object of the present invention is to provide a webbing retractor in which setting of a force limiter load is easy, and a range of setting the force limiter load can be broadened.
A webbing retractor relating to a first aspect of the present invention includes: a take-up shaft which, by being rotated in one direction, takes-up a webbing, and by being rotated in another direction, pulls-out a webbing; a pretensioner mechanism which takes-up the webbing by rotating the take-up shaft in the one direction at a time of an emergency of a vehicle; and a force limiter mechanism having an energy absorbing member which is deformable, and at a time of an emergency of the vehicle, the force limiter mechanism pulls-out the webbing by rotating the take-up shaft in the other direction by deforming the energy absorbing member by load applied to the webbing by a vehicle occupant, wherein the webbing retractor comprises: (a) a sleeve provided at the take-up shaft, and always rotating integrally with the take-up shaft; (b) a drive member having a substantially hollow cylindrical peripheral wall, and provided in a state in which the sleeve is surrounded by the peripheral wall, the drive member being rotated in the one direction by the pretensioner mechanism; (c) a hollow portion formed in the peripheral wall of the drive member, and communicating an interior portion and an exterior portion of the peripheral wall; (d) a cam plate provided in the hollow portion and able to be freely disposed at a sleeve side or at a side opposite a sleeve side; (e) a roller provided within the hollow portion between the cam plate and the sleeve, and at a time when the drive member is rotated in the one direction, when the cam plate is disposed at the sleeve side, the roller is pressed by the cam plate and engages with the sleeve; and (f) a clutch device provided at an outer periphery of the peripheral wall of the drive member in correspondence with the cam plate, and at a time when the drive member is rotated in the one direction by the pretensioner mechanism, the clutch device disposes the cam plate at the sleeve side and makes the roller engage with the sleeve so as to rotate the sleeve integrally with the drive member, and at a time when the sleeve is rotated in the other direction by the force limiter mechanism via the take-up shaft, the clutch device disposes the cam plate at the side opposite the sleeve side so as to permit relative rotation of the sleeve with respect to the drive member.
In the webbing retractor of the present invention, preferably, the clutch device includes: (a) an anchor valley formed in a configuration which is recessed toward an inner side of the drive member along a peripheral direction of an outer surface of the peripheral wall of the drive member, the anchor valley having an end portion at each of a rotating direction one direction side and a rotating direction other direction side; (b) a clutch ring formed in a substantially hollow cylindrical shape, and provided in a state of surrounding the peripheral wall of the drive member; (c) an anchor mountain formed in a configuration which protrudes toward the sleeve at an inner peripheral surface of the clutch ring in correspondence with the anchor valley, the anchor mountain being inserted into the anchor valley; (d) a recess portion formed in a configuration which is recessed toward the side opposite the sleeve side in the inner peripheral surface of the clutch ring in correspondence with the cam plate, and when the end portion of the anchor valley at the rotating direction one direction side engages with the anchor mountain, the cam plate is insertable into the recess portion; (e) a limiting device provided at the clutch ring and limiting rotation of the clutch ring in the other direction, wherein at a time when the drive member is rotated in the one direction by the pretensioner mechanism, in a state in which the drive member and the clutch ring are rotated integrally due to the end portion of the anchor valley at the rotating direction other direction side engaging the anchor mountain, the cam plate is anchored on the inner peripheral surface of the clutch ring and the cam plate is disposed at the sleeve side, and at a time when the sleeve is rotated in the other direction by the force limiter mechanism, in a state in which rotation of the clutch ring in the other direction is limited by the limiting device, the drive member is rotated by a predetermined angle in the other direction via the roller and the end portion of the anchor valley at the rotating direction one direction side engages with the anchor mountain, such that the cam plate is inserted into the recess portion and is disposed at the side opposite the sleeve side.
Further, preferably, the cam plate has, at a sleeve side side wall of the cam plate, an inclined surface which approaches the sleeve along a direction toward the rotating direction other direction side; and at a time when the drive member is rotated in the one direction by the pretensioner mechanism, in a state in which the cam plate is disposed at the sleeve side by the clutch device, the inclined surface rotates toward the one direction with respect to the roller, and the roller is pressed by the inclined surface such that the roller engages with the sleeve.
A pretensioner mechanism is provided in the webbing retractor of the present invention. When the drive member is rotated in the one direction by the pretensioner mechanism at the time of an emergency of the vehicle, the cam plate within the hollow portion of the drive member peripheral wall is disposed at the sleeve side by the clutch device. In this way, the roller between the cam plate and the sleeve is pressed by the cam plate and engages with the sleeve. As a result, the sleeve is rotated integrally with the drive member, and the take-up shaft is rotated in the one direction. Accordingly, at the time of an emergency of the vehicle, the webbing is taken-up on the take-up shaft, and slackness in the webbing is eliminated.
Further, a force limiter device is provided in the webbing retractor of the present invention. At the time of an emergency of the vehicle, due to the force limiter device, the energy absorbing member is deformed by the load applied to the webbing by the vehicle occupant, and the take-up shaft is thereby rotated in the other direction. In this way, at the time of an emergency of the vehicle, the webbing is pulled-out from the take-up shaft, and the load applied to the vehicle occupant by the webbing is limited to a given amount or less.
Here, when the take-up shaft is rotated in the other direction by the force limiter mechanism, the sleeve is rotated in the other direction. At this time, the cam plate is disposed at the side opposite to the sleeve side by the clutch device. The pressing of the roller by the cam plate is thereby cancelled, and relative rotation of the sleeve with respect to the drive member is permitted. Accordingly, when the take-up shaft is rotated in the other direction by the force limiter mechanism, the rotation of the take-up shaft is not transmitted to the drive member. In this way, even in a case in which load is applied to rotation of the drive member in the other direction, impeding of rotation of the take-up shaft in the other direction and impeding of the pulling-out of the webbing can be prevented.
Thus, it is possible for the force limiter load (the load for the webbing to be pulled out at the time of an emergency of the vehicle) to be determined only by the load for deforming the energy absorbing member. In this way, setting of the force limiter load is easy, and the range of setting of the force limiter load can be broadened.
Further, in the webbing retractor of the present invention, at the time when the drive member is rotated in the one direction by the pretensioner mechanism, the other direction side end portion of the anchor valley of the drive member engages with the anchor mountain of the clutch ring. In this way, in a state in which the drive member and the clutch ring are rotated integrally, the cam plate is anchored on the inner peripheral surface of the clutch ring, and the cam plate is disposed at the sleeve side. Accordingly, the sleeve is easily and reliably rotated integrally with the drive member, and the take-up shaft can be rotated in the one direction.
On the other hand, at the time when the sleeve is rotated in the other direction by the force limiter mechanism, in the state in which rotation of the clutch ring in the other direction is limited by the limiting device, the drive member is rotated by a predetermined angle in the other direction via the roller, and the one direction side end portion of the anchor valley of the drive member engages with the anchor mountain of the clutch ring. In this way, the cam plate is inserted into the recess portion of the clutch ring, and the cam plate is disposed at the side opposite the sleeve side. Accordingly, the pressing of the roller by the cam plate can be easily and reliably cancelled, and the sleeve can be rotated relative to the drive member.
In the webbing retractor of the present invention, an inclined surface, which approaches the sleeve along the direction toward the other direction side, is formed at the sleeve side side wall of the cam plate.
Here, when the drive member is rotated in the one direction by the pretensioner mechanism, in the state in which the cam plate is disposed at the sleeve side by the clutch device, the inclined surface of the cam plate rotates toward the one direction with respect to the roller, and the roller is pressed by the inclined surface. The roller thereby engages with the sleeve. In this way, the sleeve is even more easily and reliably rotated integrally with the drive member, and the take-up shaft can be rotated in the one direction.